Bucket unloader



Oct. 4, 1960 W. B. MCLEAN BUCKET UNLOADER Filed Oct. 30, 1958 INVENTOR.WILLIAM B- MLEAN Un t S Pat n 4"" BUCKET UNLOADER William B. McLean,Moon Township, Allegheny County, Pa, a'ssignor to Dravo Corporation,Pittsburgh, 'Pa., a corporation of Pennsylvania Filed Oct. so, 1958,Ser.No. 770,706

zclaims. (Cl. 21284) This invention relates to material handling, and isfor an improvement in unloaders of the clam shell bucket type. Morespecifically my invention is for .an improvement in apparatus of thiskind disclosed in a copending application of Howard E. Dykeman, SerialNo. 591,310,

filed June 14, 1956, now abandoned.

The aforesaid application discloses a horizontally extending boomsupported near one end on a tower. A main trolley moves horizontallyalong a trackway on this boom, and the bucket is suspended from thistrolley by cables. It is necessary that the bucket may be raised orlowered when the trolley is stationary, and that the trolley may bemoved horizontally without raising or lowering the bucket. At times bothmotions may be simultaneously necessary. The raising and lowering of thebucket isis referred to as hoisting, while the horizontal motion isreferred to as racking.

In the aforesaid Dykeman application there is disclosed a simple systemfor securing the desired operation wherein there is an auxiliary trolleyon the same track as the main trolley and the hoisting andracking cablesare engaged in pulleys on this secondary trolley in such manner that thechange in distance between the trolley and the hoisting drum, whichoccurs as the trolley moves in one direction or the other, results in amovement of the secondary trolley. The movement of the secondary trolleyis automatically coordinated to the speed of the main trolley to keepthe bucket from raising or lowering.

While the cable system shown in said application is satisfactory, thereare times when slack may suddenly develop in the lines, as for examplewhen the bucket is lowered to the ground, creating a possibility of thelines becoming fouled. An important object of the present invention isto provide a compensating cable that will assure the racking lines beingtaut at all times. Also, the cables in an unloader must be frequentlyreplaced, and the present invention further provides a power reevingarrangement for replacing the racking cable.

These and other objects and advantages are secured by my invention aswill be more fully apparent by reference to the accompanying drawings,in which the figure is a conventional view of a bucket unloader using asecondary trolley movable along the same track as the main trolley witha compensating line connected to the main trolley and passing over asheave on the secondary trolley in accordance with my invention.

Referring to the figure, 2 is a supporting tower that carries ahorizontally extending boom 3 that passes through the tower. The toweris here shown as having wheels for movement along track 4.

There is a clam shell bucket 5 suspended from a main trolley 6 by a:double cable system of cables 7 reeved' through the bucket in .awell-known manner for opening and closing the bucket. These cables areshown in dotted lines. The cables are reeved over sheaves 8 in the maintrolley 6. This trolley is movable along a trackway 9 in the boom. Thereis an auxiliary trolley 10 on the same trackway between the main trolleyand the rear Patented Oct. 4, 1960 the main trolley, and which extendsforwardly, passing around sheaves .15 at the forward end of the boom. It

then extends rearwardly above the track 9, under guide sheave 17, iswrapped around racking drum 18. From this drum it passes under guidesheave 19 and then around a sheave 20 at the very rear end of the boom.From here racking cable 14 extends forwardly to the auxiliary trolleywhere it passes around another of the sheaves at 11 on this trolley,then extends rearwardly to an anchor 21 at the rear end of the boom.

So much of the construction here described is known in the art. When theracking cable is operated to move the main carriage, .theauxiliarycarriage will move just half as far and half as fast as the maintrolley, this being the result of the racking cable passing forwardlyand then rearwardly around the sheave at 11 according to the wellknownprinciple of the pulley. At the same time, since the cables 7 passrearwardly and then forwardly around sheaves at 11, they will not raiseor lower the bucket when the main trolley is moved since the movement ofthe auxiliary trolley at half the rate and distance, resulting in thecable being taken up or paid out at the same rate as the main trolley ismoving, also in accordance with the same well-known pulley principle.

According to the present invention a compensating cable 22 is attachedto the main trolley and extends rearwardly opposite from the rackingcable 14. It passes over a sheave 23 on the auxiliary trolley and thenit extends forwardly and is anchored through a turnbuckle 24 to thetower at 25. It is adjusted so that it is always taut so that it isalways acting opposite the cable 14, keeping it also taut. It provides aconnection between the auxiliary carriage and the main carriageindependent of the connection through the bucket cables 7. Hence if thebucket is rested on the ground or elsewhere, so that the pull of itsweight is not effective to keep the cables taut, the compensating cablewill still be effective to keep the racking cable under tension andexert tension between the two trolleys. It therefore avoids thedifficulty of the cables whipping or becoming fouled when the bucketcomes suddenly to rest, and adds practically nothing to the cost of thesystem or introduces no complicated mechanism.

It will be understood that I have shown schematically only the elementsof the unloader with which my invention is concerned, the variousaccessories and controls being omitted for purposes of simplicity andclarity, and that these parts may take various forms.

I claim:

1. In a bucket unloader wherein there is a boom, a bucket-carrying maintrolley movable along the boom having sheaves thereon, a clam shell.type of bucket suspended from the trolley cables passing over thesheave to the bucket by means of which the bucket is suspended and whichare also for raising and lowering and operating the same, an auxiliarytrolley movable along the boom having sheaves thereon around which thebucket cables pass, said bucket cables extending forwardly again fromthe auxiliary trolley to a sheave located beyond the forward limit oftravel of the secondary trolley and from the last-named sheave tooperating drums, there being a racking cable attached to the maintrolley extending flqrwase iy rqmasi,eq h a t e ewest idhq the bom,thence rearwardly along theboom around a rack ing drum, the rackingcable from the'racking drum then r 4 riage around a sheave on theauxiliary carriage, then forwardly along the boom to a fixed pointforward of the forward limit of travel of theamdliary carriage and dicectqndin leye a tshsev Vet-1 1 m we t h -1 mm? X T K irq dl 1?? sanchored, the: 3 lc ahl el and bucket.- y: Carr" fte s? e s m te t n w ie mi "di b fit 1 .1 m n ann ot bu at; h l h ise j 1 1 flifi nw h Weightof the bucket exerted over thesheaves on the auxiliary nq m l -asti gimp pesi ipn -Q- e tension on the 1122; ca le-the hfi i hdafi d inventioncQm i i -a c mh ex ensliengl serwd y iw ifth m h tive' to prevent slackin the racking cable if the weight U of the :bucket is ineffective forsuch purpose.

2. The invention for an unloaderras defined in claim 1 in which means isprovided ion adjusting the tension of v the newble et mnce fi ted theleict h patent UNITED STATE-SJATENTSQ V

